Backlight device and display apparatus including the same

ABSTRACT

A backlight device includes a substrate and a plurality of light emitters on the substrate. Each of the plurality of light emitters includes a brightness controller disposed on the substrate, and a pad unit disposed on the substrate. The brightness controller generates a light-emission current, a light-emitting diode is allowed to be disposed on the pad unit, and the light-emitting diode emits light based on the light-emission current.

This application claims priority to Korean Patent Application No.10-2019-0088520, filed on Jul. 22, 2019, and all the benefits accruingtherefrom under 35 U.S.C. § 119, the content of which in its entirety isherein incorporated by reference.

BACKGROUND 1. Field

One or more embodiments relate to a backlight device and a displayapparatus including the backlight device, and more particularly, to abacklight device including a light-emitting diode (“LED”) and a displayapparatus including the backlight device.

2. Description of the Related Art

It has become essential to mount a display apparatus in an electronicdevice as one user interface. A flat-panel display is widely used as adisplay apparatus in an electronic device to make the electronic devicelight, thin, short, and small and have low power consumption.

A liquid-crystal display (“LCD”) apparatus is one type of flat-paneldisplay apparatus. The LCD apparatus is an apparatus that displays animage by adjusting amount of light proceeding from outside. Thus, theLCD apparatus includes a backlight unit including an additional lightsource for emitting light toward a liquid-crystal panel, e.g., abacklight lamp.

SUMMARY

Recently, a light-emitting diode (“LED”) having desired characteristicssuch as low power consumption, environmental friendliness, and slimdesign is widely used as a light source of a backlight unit. However, itmay be difficult for a light source including the LED to maintainuniformity of brightness and colors on a whole area of a displayapparatus. In addition, it is desired to improve instantaneous currentcontrol in the LED.

One or more embodiments relate to a backlight device with enhanceduniformity of brightness and life span.

One or more embodiments include a backlight device that may compensatefor a deviation of threshold voltage of a driving thin-film transistor.

One or more embodiments include a display apparatus including thebacklight device described above.

According to an embodiment, a backlight device includes a substrate, anda plurality of light emitters on the substrate. In such an embodiment,each of the plurality of light emitters includes a brightness controllerdisposed on the substrate, and a pad unit disposed on the substrate,where the brightness controller generates a light-emission current, alight-emitting diode is allowed to be disposed on the pad unit, and thelight-emitting diode emits light based on the light-emission current.

According to an embodiment, a backlight device includes a substrate, athin-film transistor including a semiconductor layer, a gate electrode,a first connection electrode, and a second connection electrode, whereinthe semiconductor layer is disposed on the substrate and has a firstarea and a second area, the gate electrode at least partially overlapsthe semiconductor layer, the first connection electrode is electricallyconnected to the first area, and the second connection electrode iselectrically connected to the second area, a pad unit including a firstpad and a second pad, where the second pad is connected to the firstconnection electrode, a data line disposed on the substrate, where thedata line transmits a data voltage to the gate electrode, a first powerline disposed on the substrate, where the first power line transmits afirst driving voltage to the first pad, and a second power line disposedon the substrate and connected to the second connection electrode.

According to an embodiment, a display apparatus includes a backlightunit, and a display panel disposed on the backlight unit, where aplurality of pixels is disposed in the display panel. In such anembodiment, the backlight unit includes a substrate and a plurality oflight emitters disposed on the substrate. In such an embodiment, each ofthe plurality of light emitters includes a thin-film transistor disposedon the substrate, where the thin-film transistor generates alight-emission current, a pair of pads on the substrate, and a lightemitter disposed on the pair of pads and connected to the thin-filmtransistor in series such that the light emitter emits light based onthe light-emission current.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of embodiments of the disclosure will bemore apparent from the following description taken in conjunction withthe accompanying drawings, in which:

FIG. 1 is a schematic block diagram of a backlight device according toan embodiment;

FIG. 2 is a schematic circuit diagram of a light emitter according to anembodiment;

FIG. 3 is a schematic cross-sectional view of the light emitteraccording to an embodiment;

FIG. 4 is a schematic block diagram of a backlight device according toan alternative embodiment;

FIG. 5 is a schematic block diagram of a display apparatus according toan embodiment; and

FIG. 6 is a schematic cross-sectional view illustrating a portion of thedisplay apparatus of FIG. 5.

DETAILED DESCRIPTION

The invention now will be described more fully hereinafter withreference to the accompanying drawings, in which various embodiments areshown. This invention may, however, be embodied in many different forms,and should not be construed as limited to the embodiments set forthherein. Rather, these embodiments are provided so that this disclosurewill be thorough and complete, and will fully convey the scope of theinvention to those skilled in the art. Like reference numerals refer tolike elements throughout.

It will be understood that when an element is referred to as being “on”another element, it can be directly on the other element or interveningelements may be present therebetween. In contrast, when an element isreferred to as being “directly on” another element, there are nointervening elements present.

It will be understood that, although the terms “first,” “second,”“third” etc. may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, “a first element,” “component,” “region,” “layer” or“section” discussed below could be termed a second element, component,region, layer or section without departing from the teachings herein.

Sizes of elements in the drawings may be exaggerated for convenience ofexplanation. In other words, since sizes and thicknesses of componentsin the drawings are arbitrarily illustrated for convenience ofexplanation, the present disclosure is not limited thereto.

It will be understood that when a layer, region, or component isreferred to as being “connected to” or “coupled to” another layer,region, or component, it may be “directly connected or coupled” to theother layer, region, or component, or “indirectly connected to” theother layer, region, or component with intervening elementstherebetween.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms, including “at least one,” unless the context clearly indicatesotherwise. “Or” means “and/or.” As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. It will be further understood that the terms “comprises”and/or “comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

The term “corresponding” or “in correspondence with” used herein mayspecify arrangement in or connection to a same column and/or a same rowaccording to context. For example, connection of a first member to a“corresponding” second member among a plurality of second membersindicates that the first member is connected to a second member arrangedon a same column and/or a same row as that of the first member. Forexample, when a plurality of pixels circuits and a pluralitylight-emitting diodes are arranged on a substrate in a row direction anda column direction, respectively, connection of a light-emitting diodeto a corresponding pixel circuit indicates that the light-emitting diodeis connected to a pixel circuit arranged on a same column and a same rowas those of the light-emitting diode among the plurality of pixelcircuits.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(e.g., rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein should be interpreted accordingly.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

Hereinafter, embodiments of the invention will be described in detailwith reference to the accompanying drawings.

FIG. 1 is a schematic block diagram of a backlight device according toan embodiment.

Referring to FIG. 1, an embodiment of the backlight device includes asubstrate 110 and a plurality of light emitters (referred to as “EM” inthe drawings) 120 on the substrate 110.

The substrate 110 may be an insulating substrate including a transparentglass material having silicon oxide (SiO2) as a main component or atransparent plastic material. In an embodiment, the substrate 110 may bea glass substrate or a plastic substrate. In an alternative embodiment,the substrate 110 may be a conductive substrate including a thin-filmmetal material. The substrate 110 may be a flexible substrate or a rigidsubstrate.

A buffer layer (not shown) may be disposed or arranged on the substrate110. In such an embodiment, the buffer layer effectively prevents thespread of impurity ions from the substrate 110 or penetration ofmoisture or external air from the substrate 110 and provides a flatsurface to the substrate 110. The buffer layer may include an inorganicinsulating material such as silicon oxide, silicon nitride, siliconoxynitride, aluminum oxide, aluminum nitride, titanium oxide or titaniumnitride, for example. The buffer layer may include an organic insulatingmaterial such as polyimide, polyester or acryl, for example.Alternatively, the buffer layer may include a stack including layers ofthe above-described materials or a stack including a layer including anorganic insulating material and a layer including an inorganicinsulating material.

The light emitters 120 may be disposed or arranged on the substrate 110.The light emitters 120 may be arranged substantially in a form of amatrix. The light emitters 120 may be arranged with a predeterminedinterval or a preset space therebetween in a row direction and a columndirection.

The number of the light emitters 120 is not particularly limited. In oneembodiment, for example, thousands to hundreds of thousands of lightemitters 120 may be used. In an embodiment, the number of the lightemitters 120 may be determined in a way such that each of the lightemitters 120 may be disposed or arranged on the substrate 110 toilluminate tens to hundreds of pixels when the backlight device provideslight to a display panel. Each of the light emitters 120 may include abrightness controller and a pad unit. The light emitters 120 will bedescribed in detail with reference to FIG. 2.

In an embodiment, a plurality of data lines DL, a plurality of firstpower lines PL1, and a plurality of second power lines PL2 may bedisposed or arranged on the substrate 110. The light emitters 120 may beconnected to the data lines DL, the first power lines PL1, and thesecond power lines PL2, respectively. In one embodiment, for example, adata line DL, a first power line PL1, and a second power line PL2 may beconnected to a light emitter 120. The data line DL, the first power linePL1 and the second power line PL2 respectively connected to a lightemitter 120 may be referred to as a corresponding data line DL of thelight emitter 120 among the data lines DL, a corresponding first powerline PL1 of the light emitter 120 among the first power lines PL1, and acorresponding second power line PL2 of the light emitter 120 among thesecond power lines PL2. In an embodiment, each of the data lines DL, thefirst power lines PL1, and the second power lines PL2 may be in aone-to-one correspondence with the light emitters 120. In such anembodiment, each of the numbers of the data lines DL, the first powerlines PL1, and the second power lines PL2 may be the same as the numberof the light emitters 120.

The data lines DL may transmit a data voltage for controlling brightnessof light emitted from the light emitters 120. The first power lines PL1may transmit a first driving voltage to the light emitters 120. Thesecond power lines PL2 may transmit a second driving voltage to thelight emitters 120. According to an embodiment, a level of the firstdriving voltage may be higher than a level of the second drivingvoltage, but not being limited thereto. Alternatively, the level of thesecond driving voltage may be higher than the level of the first drivingvoltage. Hereinafter, for convenience of description, embodiments inwhich a level of the first driving voltage is higher than a level of thesecond driving voltage will be described in detail. In such embodiments,the first driving voltage may be denoted, for example, as VDD, and thesecond driving voltage may be denoted, for example, as VSS.

According to an embodiment, the backlight device may further include adriving board 130. The driving board 130 may be connected to thesubstrate 110, output data voltages to the data lines DL, and providethe first and second driving voltages to the first and second powerlines PL1 and PL2, respectively. The driving board 130 may be a flexibleprinted circuit board (“FPCB”). Source integrate circuit (“IC”) chipsmay be disposed or mounted on the driving board 130, and the source ICchips may output data voltages to the data lines DL. Power pads andwires may be disposed or arranged on the driving board 130, and thepower pads receive the first and second driving voltages from outsideand the wires connect the power pads to the first and second power linesPL1 and PL2. A microcontroller, a timing controller, or the like may bedisposed or mounted on the driving board 130, and the microcontroller orthe timing controller is configured to drive a display panel.

The driving board 130 may be referred to as an external device connectedto the substrate 110 to drive the light emitters 120. In one embodiment,for example, the driving board 130 may include a first driving board anda second driving board, and source IC chips configured to output datavoltages to the data lines DL are disposed or mounted on the firstdriving board and a power chip configured to generate the first andsecond driving voltages is disposed or mounted on the second drivingboard. According to an alternative embodiment, the driving board 130 mayinclude a third driving board including a sensor configured to sense amagnitude of driving current flowing through each of the light emitters120.

FIG. 2 is a schematic circuit diagram of a light emitter 120 accordingto an embodiment.

Referring to FIG. 2, the light emitter 120 may include a brightnesscontroller 121 and a pad unit 122, on which a light-emitting diode LEDis disposed or mounted. A data line DL, a first power line PL1, and asecond power line PL2 may be connected to the light emitter 120. One ofthe light emitters 120 disposed or arranged on the substrate 110 isshown in FIG. 2. Other light emitters 120 on the substrate 110 may havesubstantially a same circuit configuration as that of the light emitter120 shown in FIG. 2.

The brightness controller 121 may include a thin-film transistor TFTconfigured to generate a light-emission current flowing from a drainelectrode DE to a source electrode SE based on a data voltage applied toa gate electrode GE via the data line DL. The thin-film transistor TFTmay generate a light-emission current with a magnitude corresponding toa level of the data voltage applied to the gate electrode GE. When alevel of the data voltage applied to the gate electrode GE becomeshigher, a light-emission current with a greater magnitude may begenerated. The light-emission current may flow from the first power linePL1 to the second power line PL2 via light-emitting diodes LED.

The thin-film transistor TFT may include the gate electrode GE, thesource electrode SE, and the drain electrode DE. The gate electrode GEmay be connected to a corresponding data line DL to thereby receive adata voltage. In an embodiment, as shown in FIG. 2, the drain electrodeDE may be connected to a cathode of the light-emitting diode LED. Thecathode of the light-emitting diode LED may be referred to as a secondelectrode. The source electrode SE may be connected to a correspondingsecond power line PL2. An anode of the light-emitting diode LED may bereferred to as a first electrode and connected to a corresponding firstpower line PL1. The drain electrode DE may be referred to as a firstconnection electrode. The source electrode SE may be referred to as asecond connection electrode.

The light-emitting diode LED is connected to the thin-film transistorTFT in series. The light-emitting diode LED emits light corresponding todriving current generated from the thin-film transistor TFT in thebrightness controller 121. In an embodiment, as shown in FIG. 2, thelight-emitting diode LED may include a plurality of light-emittingdiodes LED connected to each other in series. FIG. 2 shows an embodimentwhere two light-emitting diodes LED are connected to each other.However, this is merely exemplary. In an alternative embodiment, asingle light-emitting diode LED or three or more light-emitting diodesLED may be connected to the thin-film transistor TFT in series.Hereinafter, embodiments where two light-emitting diodes LED areconnected to each other in series will be described in detail. In anembodiment, the number of light-emitting diodes LED included in a lightemitter 120 may be variously modified in consideration of brightness ofthe light-emitting diodes LED, a driving capacity of the thin-filmtransistor TFT, and a radiation structure of the backlight device.

The pad unit 122 may include pads on which a light-emitting diode LED isdisposed or mounted. The pad unit 122 may include a pair of padsincluding a first pad and a second pad, and the first pad is connectedto a first electrode of a light-emitting diode LED and the second pad isconnected to a second electrode of a light-emitting diode LED. In anembodiment, as shown in FIG. 2, the pad unit 122 may include two pairsof pads and the two light-emitting diodes LED are disposed or mountedthereon, respectively. Each of the pair of pads may be apart from eachother to dissipate heat.

In an embodiment, as illustrated in FIG. 2, the thin-film transistor TFTmay be an n-type metal-oxide-semiconductor field-effect transistor(“MOSFET”). However, this is merely exemplary. In an alternativeembodiment, the thin-film transistor TFT may be implemented as a p-typeMOSFET. In such an embodiment, a level of the second driving voltage maybe higher than a level of the first driving voltage. In such anembodiment, connection of a light-emitting diode LED may be performed ina way opposite to the method described above. In such an embodiment, theanode of the light-emitting diode LED may be connected to the drainelectrode DE, and the cathode of the light-emitting diode LED may beconnected to the first power line PL1. In such an embodiment, thethin-film transistor implemented as the p-type MOSFET may generate alight-emission current with a great magnitude when a level of a datavoltage applied to the gate electrode GE is low. The light-emissioncurrent flows from the source electrode SE to the drain electrode DEthrough the light-emitting diodes LED.

FIG. 3 is a schematic cross-sectional view of a light emitter 120according to an embodiment.

Referring to FIGS. 2 and 3, an embodiment of the light emitter 120includes the brightness controller 121, the light-emitting diodes LED,and pads PAD on which the light-emitting diodes LED are disposed ormounted.

The brightness controller 121 may include a substrate 101, asemiconductor layer 102 on the substrate 101, a gate electrode 104, afirst connection electrode 106 c, and a second connection electrode 106d. The substrate 101 and the substrate 110 as shown in FIG. 1 may be thesame substrate or different substrates.

The substrate 101 may be a base substrate, on which the brightnesscontroller 121, including the thin-film transistor TFT, and the pad unit122 may be provided or formed by a semiconductor process. A buffer layermay be disposed or stacked on the substrate 101.

The semiconductor layer 102 includes a source area SR and a drain areaDR, each doped with an impurity to thereby have conductivity. Thesemiconductor layer 102 includes an active area Act between the sourcearea SR and the drain area DR. The drain area DR may be referred to as afirst area. The source area SR may be referred to as a second area.

In an embodiment, a polysilicon layer (not shown) may be formed bydepositing a semiconductor material layer (not shown), e.g., anamorphous silicon layer on the substrate 101, and then, crystallizingthe semiconductor material layer. Amorphous silicon may be crystallizedby using at least one of various methods such as a rapid thermalannealing (“RTA”) method, a solid-phase crystallization method (“SPC”),an excimer laser annealing (“ELA”) method, a metal-inducedcrystallization (“MIC”) method, a metal induced lateral crystallization(“MILC”) method or a sequential lateral solidification (“SLS”), forexample. The polysilicon layer formed as described above may bepatterned to form an active pattern by using a photolithography process.According to an alternative embodiment, the amorphous silicon layer maybe patterned, and then, crystallized to thereby form an active pattern.A selective ion injection process may be performed on the source area SRand the drain area DR to thereby inject an impurity. Resultantly, thesource area SR, the active area Act, and the drain area DR may be formedin the active pattern.

In an embodiment, the semiconductor layer 102 may include asilicon-based element semiconductor, but not being limited thereto. Inan alternative embodiment, the semiconductor layer 102 may include acompound semiconductor, e.g., an oxide semiconductor or an organicmaterial semiconductor.

A gate insulating layer 103 may be disposed or arranged on thesemiconductor layer 102. The gate insulating layer 103 may includeoxide, nitride, oxynitride, or a combination thereof.

A gate electrode 104 may be disposed or arranged on the gate insulatinglayer 103, and the gate electrode 104 at least partially overlaps theactive area Act of the semiconductor layer 102. A conductive materiallayer (not shown) is disposed or stacked on the gate insulating layer103. The conductive material layer may be patterned to form the gateelectrode 104 through a photolithography process and an etching process.The gate electrode 104 may include a metal or an alloy of metal such asmolybdenum (Mo), molybdenum tungsten (MoW), an aluminum (Al)-basedalloy, or the like, but not being limited thereto. Alternatively, thegate electrode 104 may have a stacked structure including Mo/Al/Mo.

The gate electrode 104 may function as a mask in a process of injectingan impurity into the source area SR and the drain area DR. The activearea Act is the semiconductor layer 102 between the source area SR andthe drain area DR. The active area Act may be defined as a portionoverlapping the gate electrode 104.

An interlayer insulating layer 105 may be disposed or arranged on thegate electrode 104. Contact holes may be defined in the gate insulatinglayer 103 and the interlayer insulating layer 105, where the contactholes respectively expose the source area SR and the drain area DR ofthe semiconductor layer 102.

An electrode material layer may be disposed or stacked on the interlayerinsulating layer 105. The electrode material layer may include a metalsuch as Mo, chromium (Cr), tungsten (W), aluminum-neodymium (Al—Nd),titanium (Ti), MoW, or Al.

The electrode material layer may be patterned as a first wire 106 a, asecond wire 106 b, a first connection electrode 106 c, and a secondconnection electrode 106 d. The first connection electrode 106 c and thesecond connection electrode 106 d may be connected to the drain area DRand the source area SR, respectively, via the contact holes in the gateinsulating layer 103 and the interlayer insulating layer 105.

An end of the first wire 106 a and an end of the second wire 106 b mayconstitute a pair of pads PAD on which the light-emitting diode LED maybe disposed or mounted. The end of the first wire 106 a may be referredto as a first pad. The end of the second wire 106 b may be referred toas a second pad. Another end of the second wire 106 b and an end of thefirst connection electrode 106 c may also constitute a pair of pads PADon which the light-emitting diode LED may be disposed or mounted. Theother end of the second wire 106 b may be referred to as a first pad.The end of the first connection electrode 106 c may be referred to as asecond pad. The first connection electrode 106 c may connect the secondpad to the drain area DR. The first pad may be connected to a firstelectrode of the light-emitting diode LED, e.g., an anode. The secondpad may be connected to a second electrode of the light-emitting diodeLED, e.g., a cathode.

A protective layer 107 may be disposed or arranged on the first wire 106a, the second wire 106 b, the first connection electrode 106 c, and thesecond connection electrode 106 d to expose the pads PAD. The protectivelayer 107 may be referred to as a planarization layer or a passivationlayer. The protective layer 107 may include an inorganic insulatingmaterial or an organic insulating material.

The light-emitting diodes LED may be disposed or mounted on the pair ofpads PAD, respectively. The light-emitting diode LED may be asmall-sized light-emitting diode. Although not illustrated in FIG. 3,the first wire 106 a may be connected to the first power line PL1, andthe second connection electrode 106 d may be connected to the secondpower line PL2. The gate electrode 104 may be connected to the data lineDL.

Although not illustrated in FIG. 3, auxiliary wires on a same layer asthe gate electrode 104 may be disposed or arranged below the first wire106 a and the second wire 106 b. The auxiliary wires may be connected tothe first wire 106 a and the second wire 106 b via a contact plug.

FIG. 4 is a schematic block diagram of a backlight device according toan alternative embodiment.

Referring to FIG. 4, an embodiment of the backlight device includes thesubstrate 110, the light emitter 120 on the substrate 110, and thedriving board 130. For convenience of illustration, FIG. 4 shows only asingle light emitter 120 is disposed on the substrate 110. However, asshown in FIG. 1, the plurality of light emitters 120 may be arranged onthe substrate 110 in a matrix form. The light emitters 120 aresubstantially same as those described above with reference to FIGS. 2and 3, and any repetitive detailed description thereof will be omitted.For convenience of illustration, FIG. 4 shows a single data line DL, asingle first power line PL1, and a single second power line PL2, eacharranged on the substrate 110 and connected to the light emitter 120.However, as shown in FIG. 1, a plurality of the data lines DL, aplurality of the first power lines PL1, and a plurality of the secondpower lines PL2 may be connected to the plurality of light emitters 120.

The driving board 130 may include a voltage controller 132, a powersupply 131, and a sensor 133. The driving board 130 includes a firstresistor R1 and a second resistor R2 connected to each other in seriesbetween the second power line PL2 and the power supply 131. In anembodiment, where the second power line PL2 is provided in plural, thedriving board 130 may include a plurality of first resistors R1 and aplurality of second resistor R2.

The power supply 131 may supply a first driving voltage VDD to the firstpower lines PL1 and supply a second driving voltage VSS to the secondpower lines PL2. The power supply 131 may generate the first drivingvoltage VDD and the second driving voltage VSS. According to analternative embodiment, the power supply 131 receive the first drivingvoltage VDD and the second driving voltage VSS from an outside andtransmit the first driving voltage VDD and the second driving voltageVSS to the first power lines PL1 and the second power lines PL2,respectively.

The voltage controller 132 may output a data voltage to each of the datalines DL. The voltage controller 132 may control light-emissionbrightness of the light emitters 120 by controlling a level of the datavoltage. According to an embodiment, some areas of the display panel maybe desired to display full black. In such an embodiment, the voltagecontroller 132 may provide a non-light-emission data voltage to thelight emitters 120 corresponding to areas where full black is to bedisplayed. Thus, the partial areas may display full black without anyleakage of light.

A voltage of a sensing node Ns between the first resistor R1 and thesecond resistor R2 may be sensed by the sensor 133. A voltage drop isreflected in a voltage of the sensing node Ns, and the voltage dropcorresponds to a value obtained by multiplying driving current generatedby the thin-film transistor TFT by a resistance value of the secondresistor R2. The sensor 133 may sense a magnitude of the driving currentbased on the voltage of the sensing node Ns. The sensor 133 may provideinformation about the sensed voltage of the sensing node Ns or thesensed magnitude of the driving current to the voltage controller 132.The voltage controller 132 may adjust a level of a data voltage based onthe information about the voltage of the sensing node Ns or themagnitude of the driving current.

In one embodiment, for example, the light emitters 120 may be configuredto emit light with brightness of 100 when the voltage controller 132applies a data voltage (e.g., 5 volts (V)) to the light emitters 120.When a magnitude of driving current sensed by the sensor 133 is amagnitude of current corresponding to brightness of 90, the voltagecontroller 132 may increase a magnitude of the data voltage applied tothe light emitters 120 so that the light emitters 120 emit light withbrightness of 100. Such a process may be performed in real time. In oneembodiment, for example, the voltage controller 132 may increase ordecrease a data voltage until a magnitude of driving current sensed bythe sensor 133 becomes a magnitude of current corresponding to targetbrightness. The voltage controller 132 may be implemented as a source IChaving a plurality of channel so that a plurality of data voltages areoutput to the plurality of data lines DL.

Thin-film transistors TFT may have different threshold voltages due to amanufacture tolerance, for example. In addition, a magnitude of athreshold voltage may vary with time depending on deterioration.According to an embodiment, a magnitude of driving current generated bythe thin-film transistors TFT may be sensed and, the data voltage may beadjusted based on the sensed magnitude of the driving current. Thus, thelight emitters 120 may emit light with accurate brightness. In such anembodiment, resistance values of the second resistors R2 may beidentical to each other.

Resistance values of the first resistors R1 may be different from eachother. In an embodiment, lengths of the first power lines PL1 and thesecond power lines PL2 may be different from one another according topositions of the light emitters 120 on the substrate 110. In oneembodiment, for example, lengths of the first power lines PL1 and thesecond power lines PL2 connected to the light emitters 120 locatedadjacent to the driving board 130 may be relatively small, such that asum of line resistances of the first power line PL1 and the second powerline PL2 may be relatively small. In such an embodiment, lengths of thefirst power line PL1 and the second power line PL2 connected to thelight emitters 120 located far from the driving board 130 may berelatively great, such that a sum of line resistances of the first powerline PL1 and the second power line PL2 may be relatively great. Thefirst resistors R1 may have resistance values for compensating for thesum of the line resistances of the first power line PL1 and the secondpower line PL2.

In an embodiment, a resistance value of the first resistor R1 may bedesigned so that a sum of a resistance value of the first power linePL1, a resistance value of the second power line PL2, and a resistancevalue of the first resistor R1 is constant for the light emitters 120 indifferent positions. Accordingly, a voltage of the sensing node Nssensed by the sensor 133 may accurately reflect driving current flowingthrough all the light emitters 120. According to an alternativeembodiment, a sum of lengths of the first power line PL1 and the secondpower line PL2 for the light emitters 120 in different positions may bedesigned to be constant so that a resistance value of the first powerline PL1 and a resistance value of the second power line PL2 areconstant. In such an embodiment, at least one of the first power linePL1 and the second power lines PL2 may have a zigzag shape to increase aresistance value.

FIG. 4 shows an embodiment where the power supply 131, the voltagecontroller 132, and the sensor 133 are disposed or mounted on orincluded in one driving board 130. However, this is merely exemplary. Inan alternative embodiment, the voltage controller 132 may be disposed ormounted on the driving board 130, while a power generator configured togenerate the first and second driving voltages VDD and VSS and thesensor 133 may be disposed or mounted on a driving board configured todrive the display panel. In an embodiment, a driving board constitutingthe backlight device and the driving board configured to drive thedisplay panel may be integrated as a single driving board.

FIG. 5 is a schematic block diagram of a display apparatus 1000according to an embodiment.

Referring to FIG. 5, an embodiment of the display apparatus 1000includes a backlight unit 100 and a display panel 200. The display panel200 is disposed or arranged on the backlight unit 100. A plurality ofpixels may be disposed or arranged in the display panel 200.

The backlight unit 100 may correspond to the backlight device of FIGS. 1to 4. The backlight unit 100 includes a substrate and a plurality oflight emitters on the substrate.

Each of the light emitters is disposed or arranged on the substrate.Each of the light emitters includes a thin-film transistor, a pair ofpads on the substrate, and a light emitter. In such an embodiment, thethin-film transistor generates a light-emission current and the lightemitter is disposed or mounted on the pair of pads and connected to thethin-film transistor in series to thereby emit light corresponding tothe light-emission current.

As light is emitted from the light emitters of the backlight unit 100toward the display panel 200 and a light transmittance of pixels isadjusted based on received image data, the display panel 200 may displayan image. The display panel 200 may be a liquid-crystal display panelincluding a liquid-crystal layer.

The controller 300 may drive the backlight unit 100 and the displaypanel 200. The controller 300 may include the voltage controller 132 andthe sensor 133, as shown in FIG. 4. The controller 300 may include atiming controller (not shown), a scan driver and a data driver, and thetiming controller drives the display panel 200. The controller 300 mayfurther include the power supply 131 of FIG. 4.

FIG. 6 is a schematic cross-sectional view illustrating a portion of adisplay apparatus 1000 of FIG. 5.

Referring to FIGS. 5 and 6, an embodiment of the display apparatus 1000includes the backlight unit 100 and the display panel 200, which is aliquid-crystal display panel on the backlight unit 100. In anembodiment, the display apparatus 1000 may include a color filter (notshown) disposed or arranged between the backlight unit 100 and theliquid-crystal display panel 200 or on the liquid-crystal display panel200.

The backlight unit 100 may provide light L for displaying an image onthe liquid-crystal display panel 200. The backlight unit 100 includesthe substrate 110 and the plurality of light emitters 120 on thesubstrate 110. The light emitters 120 respectively include thelight-emitting diode LED, the pad unit 122, and the brightnesscontroller 121. In such an embodiment, the light-emitting diode LEDemits the light L, the light-emitting diode LED is disposed or mountedon the pad unit 122, and the brightness controller 121 controlsbrightness of the light-emitting diode LED.

The liquid-crystal display panel 200 includes a lower substrate 210, apixel circuit 220 on the lower substrate 210, the pixel electrode 230,the liquid-crystal layer 240, and a common electrode 250. The pixelcircuit 220 includes first to third pixels PX1, PX2, and PX3. Each ofthe first to third pixels PX1, PX2, and PX3 controls the pixel electrode230 disposed or arranged thereon.

The lower substrate 210 may include a glass or a transparent plasticmaterial. A lower polarizer (not shown) may be disposed or arranged on alower surface of the lower substrate 210, and the lower polarizertransmits only light of particular polarization, among light emittedfrom the backlight unit 100. In one embodiment, for example, the lowerpolarizer may be a polarization plate configured to transmit lightline-polarized in a first direction.

The pixel circuit 220 may include a plurality of thin-film transistors(not shown), and a gate line and a data line configured to apply a gatesignal and a data signal, respectively, to the plurality of thin-filmtransistors.

The pixel electrode 230 may be connected to a source or drain electrodeof the thin-film transistor in the pixel circuit 220 to thereby receivea data voltage.

The common electrode 250 may be disposed or arranged on theliquid-crystal layer 240. An upper polarizer (not shown) may be disposedor arranged on the common electrode 250. The upper polarizer may be apolarization plate configured to transmit light of line polarization ina second direction perpendicular to light of line polarization in afirst direction transmitted by the lower polarizer. However, this ismerely exemplary. Alternatively, both of the upper polarizer and thelower polarizer may be configured to transmit light of samepolarization.

The liquid-crystal layer 240 is disposed or arranged between the pixelelectrode 230 and the common electrode 250. In an embodiment,arrangement of liquid-crystal molecules in the liquid-crystal layer 240is adjusted based on a voltage applied between the pixel electrode 230and the common electrode 250. In such an embodiment, an area of theliquid-crystal layer 240 between the pixel electrode 230 and the commonelectrode 250 is controlled, based on a voltage applied between thepixel electrode 230 and the common electrode 250, to a turn-on mode inwhich polarization of incident light is changed or a turn-off mode inwhich polarization of incident light is not changed. In an embodiment, adegree in which polarization of incident light is changed is adjusted sothat an intermediate gray scale may be represented.

As the light L controlled by the liquid-crystal layer 240 on the firstpixel PX1 passes through a first color filter layer, the light L isdisplayed as light of a first color (e.g., red). As the light Lcontrolled by the liquid-crystal layer 240 on the second pixel PX2passes through a second color filter layer, the light L is displayed aslight of a second color (e.g., green). As the light L controlled by theliquid-crystal layer 240 on the third pixel PX3 passes through a thirdcolor filter layer, the light L is displayed as light of a third color(e.g., blue).

When the light L emitted from the backlight unit 100 is provided to theliquid-crystal display panel 200, the light L passing through theliquid-crystal display panel 200 may be selectively transmitted orblocked in each pixel area based on image information to thereby beselectively incident on a color filter. The color filter selectivelytransmits only some colors of the light L that passed through theliquid-crystal display panel 200 according to the pixel PX1, PX2, or PX3so that a color image may be displayed.

According to embodiments, pads and a thin-film transistor are disposedor arranged directly on a glass substrate, a light-emitting diode may bedisposed or mounted on the pads and the thin-film transistor may controlbrightness of a light-emitting diode. Thus, a manufacture cost may bereduced, and product reliability and life-span may be enhanced. Adeviation of a voltage drop and a deviation of a threshold voltage of athin-film transistor due to length difference between wires may beeffectively compensated. Thus, brightness uniformity of a backlightdevice may improve. According to embodiments, a display apparatusincluding a backlight unit in which brightness uniformity is improvedmay enhance display quality.

It should be understood that embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments. While one or more embodiments have beendescribed with reference to the figures, it will be understood by thoseof ordinary skill in the art that various changes in form and detailsmay be made therein without departing from the spirit and scope asdefined by the following claims.

What is claimed is:
 1. A backlight device comprising: a substrate; and aplurality of light emitters on the substrate, wherein each of theplurality of light emitters comprises: a brightness controllercomprising a thin-film transistor disposed on the substrate, wherein thethin-film transistor generates a light-emission current with a magnitudecorresponding to a level of a data voltage applied to the thin-filmtransistor; and a pad unit disposed on the substrate, wherein alight-emitting diode is disposed on the pad unit, and the thin-filmtransistor drives the light-emitting diode to emit light based on thelight-emission current.
 2. The backlight device of claim 1, wherein thethin-film transistor comprises: a semiconductor layer disposed on thesubstrate and including a first area and a second area; a gate electrodeat least partially overlapping the semiconductor layer; a firstconnection electrode electrically connected to the first area; and asecond connection electrode electrically connected to the second area,and the thin-film transistor generates the light-emission current withthe magnitude corresponding to the level of the data voltage applied tothe gate electrode.
 3. The backlight device of claim 2, wherein the padunit comprises a first pad to be connected to a first electrode of thelight-emitting diode, and a second pad connected to the first connectionelectrode and to be connected to a second electrode of thelight-emitting diode.
 4. The backlight device of claim 3, furthercomprising: a plurality of data lines on the substrate; a plurality offirst power lines on the substrate; and a plurality of second powerlines on the substrate, wherein each of the plurality of light emittersis connected to a corresponding data line from among the plurality ofdata lines, a corresponding first power line from among the plurality offirst power lines, and a corresponding second power line from among theplurality of second power lines.
 5. The backlight device of claim 4,wherein the corresponding data line is connected to the gate electrode,the corresponding first power line is connected to the first pad, andthe corresponding second power line is connected to the secondconnection electrode.
 6. The backlight device of claim 5, furthercomprising: a driving board connected to the substrate, wherein thedriving board comprises: a voltage controller which outputs the datavoltage to the corresponding data line; and a power supply which outputsa first driving voltage to the corresponding first power line and asecond driving voltage to the corresponding second power line.
 7. Thebacklight device of claim 6, wherein the driving board further comprisesa first resistor and a second resistor connected to each other in seriesbetween the corresponding second power line and the power supply.
 8. Thebacklight device of claim 7, wherein the driving board further comprisesa sensor which senses a voltage of a sensing node between the firstresistor and the second resistor.
 9. The backlight device of claim 8,wherein the voltage controller adjusts a level of the data voltage basedon the voltage of the sensing node sensed by the sensor.
 10. Thebacklight device of claim 7, wherein the first resistor has a resistancevalue corresponding to a distance between a light emitter correspondingthereto and the power supply, and the light emitter corresponding to thefirst resistor is connected to the first resistor between thecorresponding second power line and the power supply via thecorresponding second power line.
 11. The backlight device of claim 1,wherein the pad unit is provided in plural such that a plurality oflight-emitting diodes is disposed thereon, and the plurality oflight-emitting diodes is connected to one another in series and emitslight based on the light-emission current.
 12. A backlight devicecomprising: a substrate; a thin-film transistor comprising asemiconductor layer, a gate electrode, a first connection electrode, anda second connection electrode, wherein the semiconductor layer isdisposed on the substrate and includes a first area and a second area,the gate electrode at least partially overlaps the semiconductor layer,the first connection electrode is electrically connected to the firstarea, and the second connection electrode is electrically connected tothe second area; a pad unit comprising a first pad and a second pad,wherein the second pad is connected to the first connection electrode; adata line disposed on the substrate, wherein the data line transmits adata voltage to the gate electrode; a first power line disposed on thesubstrate, wherein the first power line transmits a first drivingvoltage to the first pad; and a second power line disposed on thesubstrate and connected to the second connection electrode.
 13. Thebacklight device of claim 12, further comprising a light-emitting diodedisposed on the first pad and the second pad, wherein a first electrodeof the light-emitting diode is connected to the first pad, and a secondelectrode of the light-emitting diode is connected to the second pad.14. The backlight device of claim 12, further comprising: a firstresistor connected between the second power line and a sensing node; anda second resistor connected between the sensing node, and a node towhich a second driving voltage is applied.
 15. The backlight device ofclaim 14, wherein a resistance value of the first resistor decreases asa sum of a length of the first power line and a length of the secondpower line increases.
 16. The backlight device of claim 14, furthercomprising a voltage controller adjusts a level of the data voltagebased on a voltage of the sensing node.
 17. The backlight device ofclaim 12, further comprising: a plurality of light emitters disposed onthe substrate, wherein each of the plurality of light emitters comprisesthe thin-film transistor and the pad unit.
 18. A display apparatuscomprising: a backlight unit; and a display panel disposed on thebacklight unit, wherein a plurality of pixels are disposed in thedisplay panel, wherein the backlight unit comprises a substrate and aplurality of light emitters disposed on the substrate, and each of theplurality of light emitters comprises: a thin-film transistor disposedon the substrate, wherein the thin-film transistor generates alight-emission current, and the thin-film transistor generates thelight-emission current with a magnitude corresponding to a level of adata voltage applied to the thin-film transistor; a pair of pads on thesubstrate; and a light emitter disposed on the pair of pads andconnected to the thin-film transistor in series such that the thin-filmtransistor drives the light emitter to emit light based on thelight-emission current.
 19. The display apparatus of claim 18, whereinthe thin-film transistor comprises: a semiconductor layer disposed onthe substrate and including a first area and a second area; a gateelectrode at least partially overlapping the semiconductor layer; afirst connection electrode connected between the first area and a padamong the pair of pads; and a second connection electrode electricallyconnected to the second area, and the thin-film transistor generates thelight-emission current with the magnitude corresponding to the level ofthe data voltage applied to the gate electrode.
 20. The displayapparatus of claim 19, wherein the backlight unit further comprises: afirst resistor and a second resistor connected to each other in seriesand to the second connection electrode; and a voltage controller whichadjusts a level of a data voltage to be applied to the gate electrodebased on a voltage of a sensing node between the first resistor and thesecond resistor.